1. Field of the Invention
This invention relates to a method of repairing and removing scratches from an optically-read disc, e. g., compact discs (often called “CD's” or “DVD's”). More specifically, this invention provides a method and apparatus for refurbishing the surface of a disc such that when refurbished, an optical reader, which uses a laser to read digital information stored on the disc, can read the digital information on the disc without the optical distortion caused by a scratch and like surface imperfection.
2. Description of Related Art
Optically read digital storage and play-back media, such as laser discs, compact audio discs, digital video discs, CD-ROM's (i.e., read only memory) and others, hereinafter collectively referred to as compact discs (i.e., “CD's”), are essentially various layers of plastic covering which protect a reflective foil coating. The metallic foil coating may be configured to store a wide variety and quantity of digital information which may be optically read through the use of one or more laser beams or other light amplified beams.
The compact disc, as currently manufactured, is round and comprised of a synthetic material (e.g., polycarbonate), with a typical diameter of the disc being about 4¾ inches and a typical thickness being about 1/16 inches. The disc size varies slightly as to CD's and DVD's. The disc typically has a center aperture approximately ⅝ inches in diameter for receiving a centering spindle in a playback apparatus. Digitally recorded material typically extends on one or both sides of the disc from a data band extending about ¾ inches from the center aperture outward to within about ¼ inch of the peripheral end of the disc. A bearing or contact area may extend on one or both sides, in approximately the same dimensions, for bearing on a playback apparatus, which spins the disc at high speed.
The digital information is contained on a relatively thin layer of metallic material sandwiched in a protective layer of the synthetic material (e.g., the polycarbonate). A laser within the playback apparatus reads the digital information through the plastic layer. If the plastic layer becomes scratched, stained or pitted, the laser light will distort and not accurately read the digital information.
Unless the disc can in some way be refurbished or reconditioned, the disc would have to be thrown away. Due to the high cost of a digital disc, a need exists for an inexpensive means for refurbishing and/or reconditioning the scratched protective surface of the disc.
One known process for reconditioning digital recording discs involves a motorized apparatus having a buffing surface that abrades the protective surfacein a generally uniform manner across the surface area of the disc. While this method may effectively repair the protective surface of some discs, it can leave fine abrasions on other discs, which abrasions can fall into alignment with the spiral data track or otherwise affect the quality of the treated disc so that playability is not restored.
Also, reconditioning by the use of a buffer may leave a sudden or stepwise change between the thickness of an unconditioned portion of the protective surface and a reconditioned portion of the protective surface. A laser beam passing through this sharp demarcation may be undesirably bent or scattered so that the underlying data track or tracks cannot be detected by the playback system.
As such, the buffing technique selectively abrades one area more another area, thus requiring fine manipulation of the buffer relative to the CD. This is very labor intensive and the reconditioning depends on the skill of the worker performing the reconditioning.
Another approach for reconditioning scratched plastic surfaces involves filling the scratch or void with a mixture having the same refractive index. As understood, this method has been used with limited success in glazed canopies of helicopters, but not with CD's.
U.S. Pat. No. 6,277,309, issued Aug. 21, 2001 to Campbell, discloses a process and device for resurfacing damaged compact discs by melting a thin layer of the optical surface of the compact disc so that it reflows and fills any scratches or other imperfections. Campbell passes the CD beneath a burner that generates flames, with the flames therefrom operating to melt a very thin layer of the layer forming the protective optical surface above the foil. This melted layer then flows into the scratches formed in the optical surface and creates a smooth reconditioned surface.
Because uniform distribution of the heat is essential, Campbell suggests that the burner and the disc may be rotated relative to one another.
The use of a flame is believed to possibly degrade the optical surface or simply burn the disc up. At the least, the Campbell solution is labor intensive and requires an experienced worker to position and adjust the flame relative to the disc. At the worst, the Campbell approach will destroy the disc sought to be reconditioned.
A primary object and advantage of this invention is the provision of a cost effective method and apparatus that overcomes the disadvantages of the prior art.
A further object and advantage of this invention of this invention is the provision of a method and apparatus that restores a compact disc, as close as possible, to its original or new condition.
Another object and advantage of this invention is the provision of a method and apparatus, which may be repeated several times without wearing away, or otherwise degrading, the optical surface of the disc that is to be restored.
Yet a further object and advantage of this invention is the provision of a method and apparatus for refurbishing the optical quality of a compact disc that is inexpensive and capable of being performed by less skilled workers.
Still a further object and advantage of this invention is the provision of a method and apparatus for restoring the optical surface of a compact disc that is repeatable with and yields uniformity of results